The atomic-primops package

After GHC 7.4 a new casMutVar# primop became available, but it's
difficult to use safely, because pointer equality is a highly
unstable property in Haskell. This library provides a safer method
based on the concept of Tickets.

Also, this library uses the foreign primop capability of GHC to
add access to other variants that may be of
interest, specifically, compare and swap inside an array.

Changes in 0.3:

Major internal change. Duplicate the barrier code from the GHC RTS and thus
enable support for executables that are NOT built with -threaded.

Changes in 0.4:

Further internal changes, duplicate cas routine well as barriers.

Add fetchAddByteArrayInt

Add an Unboxed counter variant that uses movable ByteArrays on the GHC heap.